This invention relates to machine building for construction, road-building and melioration works and, in particular, to automated planers used to plane the surface of the ground.
There are known trailer long-wheelbase planers (the wheelbase is the distance between the fore and rear axles), comprising hinged fore and rear frames and a scoop with a cutting edge mounted on the fore frame, running gear and hydraulic cylinders.
Long-wheelbase planers feature a wheelbase of 15-18 m, which is required to ensure adequate planing of the ground surface. Such machines are heavy and difficult to maneuver and cannot be employed in restricted conditions, e.g. for rice fields planing.
Besides, the forementioned planers are equipped with a bottomless scoop featuring an immovable rear wall and the entire mass of scooped earth is dragged over the ground surface, which involves increased resistance to the planer movement. In case the tractor thrust force is limited, this results in less earth volume in the scoop and, consequently, reduces the quality of planing, when filling up recesses, constituting a major drawback of such a planer.
There is known a trailer long-wheelbase planer, eliminating this drawback. This planer is equipped with a scoop featuring a swivel wall hinged to an underblade plate actuated by a pulley-and-rope system. This design is deficient in that it demands great consumption of energy per unit of planed ground area, involves lifting considerable amounts of earth masses, and nonuniform recess filling on the planed area.
In all the forementioned trailer long wheelbase planers the height of the scoop in relation to the wheels is adjusted manually resulting in sharp decrease of efficiency.
Also planers are known which are equipped with automatic devices for the scoop height adjustment. Employment of automatic devices permits a wheelbase of a planer with its planing efficiency kept on the same level (or even raised).
This is, for example, an automatic system for a planer working member control. This system comprises two adjustment circuits composed of a dip angle pickup, electrohydraulic distributors and a contact device, which operates depending on the reciprocal position of fore and rear indication struts, making the system complicated and insufficiently reliable in operation.
It is known that dip angle pickups are sensitive to inertial forces acting in the plane of the measured angle. Such forces may occur in irregular planer movement, particularly when the tractor towing the planer starts or stops. The pickup produces false signals in this case, which results in worse planing characteristics of the planer and is also a drawback of such an automatic system.